1. Field of the Invention
The invention concerns a device for cleaning metal surfaces after they have been worked at high temperatures, that is, an apparatus with which scabs, oxidation or other marks left by high temperature treatment, such as the welding of metals and laser or plasma cutting, can be removed.
2. Description of the Prior Art
Prior art comprises a device consisting of a fibreglass pad wound around an electrode in the form of a nib. The pad is dipped into an acid solution of phosphoric acid (81% by weight), quinoline (0.01% by weight) and water and then placed near the surface that is to be treated: a power supply of low voltage alternate current is applied, with the ground conductor connected to the piece and the other connected to the metal part of the pad's support. The conditions of an electrolytic cell are thus created in the solution which can then remove the oxide or scab in a short time.
However, with this type of device, the operator is frequently hampered by technical difficulties with the maintenance and replacement of the insulating fibreglass material as, being exposed to very high temperatures, it can burn, and as a considerable quantity of dirt gets caught up in the fabric, hindering the development of suitable electric conditions, also as the pad must frequently be dipped into the acid solution: if it is not sufficiently damp, the material may become physically damaged and the electrolytic action is reduced.
Moreover, the residue remains firmly attached to the treated surface requiring several washes before being dried.
Furthermore, care has to be taken with the acid solution, which has a high density, to prevent it from dripping onto the operator or onto the floor when applied to vertical or underside surfaces.
Finally, it is not very practical for the operator to work next to a container filled with an acid solution and a great amount of the fibreglass insulating fabric that has to be wound around the nib of the electrode, in as much as work is not continuous, and thereby not productive, and it can also be dangerous.
Prior art also comprises a device for cleaning metals with fluid acid solutions--based on citric acid--which are constantly conveyed to the pad by means of an electric pump placed in the container of the acid solution.
However, owing to the low power levels employed and the low aggressiveness of the acid solution, this device has never been widely used in industry.
Furthermore, the metal electrode through which current flows and which is wrapped in the pad heats up because it is a good conductor of heat as well as of electricity: the increase in the electrode's temperature due to the accumulation of heat in the pad makes the acid solution evaporate quickly and can even cause the pad to burn, causing a short circuit between the electrode and the surface being treated. For this reason the pad has to be replaced relatively often.
Finally, none of the prior art devices protect the operator from the fumes generated during the cleaning process.
Such prior art may be subject to considerable improvement with a view to eliminating the said drawbacks, to increasing the safety of the device, its ease of use and to increasing the service life of the pad.